Maria, a drug-addicted sex worker, rests between clients in the room she rents in Kryvyi Rih, Ukraine. The country has the highest incidence of HIV/Aids in Europe and, according to a UNICEF report, one in five sex workers is living with HIV. Maria says she remains HIV negative.

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Brent Stirton is the senior photographer for the assignment division of Getty Images, New York. He specializes in documentary work, and is known for his alternative approaches. He travels an average of nine months of the year on assignment, spending most of his time working for National Geographic magazine.